In classical interferometry measurement techniques, measurement dynamic range and accuracy are very limited. High accuracy can be achieved over just a small range of depth.
Moire technique measurements are more suited to measuring objects that are nearly two-dimensional, and require high frequency fringes for both projection and reference, making alignment and phase shifting problematic.
Photogrammetry measurement techniques are very slow and labor intensive, and provide high accuracy measurement for only a sparse set of points on a surface.
The present invention overcomes these disadvantages, by providing high accuracy depth measurements over a large range of depth. Measurement accuracy is assured through a reliable calibration procedure. This calibration procedure does not require tight alignment tolerances or assume ideal alignment. The measurement data for a surface are at very high resolution, to provide a full three-dimensional surface image. Measurements and data processing are done quickly. The projection system can use white light, which does not suffer from coherent light effect problems. Coarse gratings can be used with direct fringe line projection, reducing alignment and optical quality requirements, and minimizing phase shifting motion accuracy requirements. Temporal phase shifting provides high resolution three-dimensional measurements. Spatial phase shifting provides a high-speed (virtually instantaneous) measurement capability with some reduction in resolution.